Methods for converting lower alkanes and alkanes to alcohols and diols

Abstract

The present invention is directed to methods for converting lower alkanes and alkenes to the corresponding lower alkanols and diols. In the methods of the present invention, a gaseous halogen, preferably bromine, is produced by decomposing a metal halide in a liquid having a melting point below and a boiling point above the decomposition temperature of the metal halide. The preferred liquid is molten, hydrated ferric chloride maintained at a temperature between about 37-280° C. The lower alkane or alkene is halogenated in a gas phase reaction with the produced halogen. The alkyl halide or alkyl dihalide is contacted with a metal hydroxide, preferably an aqueous solution of ferric hydroxide, to regenerate the metal halide and produce the corresponding lower alkanol or diol. The present invention is particularly efficient for converting methane to methanol using ferric bromide to provide the halogen.

What is claimed is: 
     
       1. A method for converting methane to methanol, comprising: decomposing ferric bromide from a molten mixture of ferric bromide and hydrated ferric chloride to produce bromine gas and ferrous bromide;   reacting said bromine gas with methane to produce methyl bromide and hydrogen bromide gases; and   passing said gases through an aqueous solution of ferric hydroxide to produce methanol and to regenerate said ferric bromide.   
     
     
       2. The method of claim 1 wherein said ferrous bromide is dissolved in water and oxidized to regenerate said ferric bromide and to produce said aqueous solution of ferric hydroxide. 
     
     
       3. The method of claim 2 wherein said molten mixture is maintained at a temperature of about 110-280° C. 
     
     
       4. The method of claim 3 wherein said bromine and methane are reacted at a temperature greater than about 250° C. 
     
     
       5. The method of claim 2 wherein said solution is maintained at a temperature of about 40-80° C. 
     
     
       6. A method for producing a lower alkanol from a corresponding lower alkane, comprising: producing a gaseous halogen by decomposing a metal halide in a liquid, said liquid having a melting point below and a boiling point above the decomposition temperature of said metal halide;   reacting said halogen with a lower alkane to produce an alkyl halide and hydrogen halide gases; and   reacting said gases with a metal hydroxide to regenerate said metal halide and to produce a lower alkanol corresponding to said alkane.   
     
     
       7. The method of claim 6 wherein said halogen is bromine. 
     
     
       8. The method of claim 6 wherein said gases are passed through an aqueous solution of said metal hydroxide. 
     
     
       9. The method of claim 8 wherein said metal halide decomposes to produce a metal halide of a lower oxidation state which is dissolved in water and oxidized to regenerate said metal halide and to produce said aqueous solution of metal hydroxide. 
     
     
       10. The method of claim 6 wherein said alkane has from 1 to 5 carbon atoms. 
     
     
       11. The method of claim 6 wherein said metal halide is ferric bromide, said liquid is molten, hydrated ferric chloride, and said metal hydroxide is ferric hydroxide. 
     
     
       12. The method of claim 11 wherein said gases are passed through an aqueous solution of ferric hydroxide. 
     
     
       13. The method of claim 12 wherein said solution is maintained at a temperature of about 40-80° C. 
     
     
       14. The method of claim 11 wherein said liquid is maintained at a temperature of about 110-280° C. 
     
     
       15. The method of claim 11 wherein said halogen and lower alkane are reacted at a temperature greater than about 250° C. 
     
     
       16. A method for producing a lower diol from a corresponding alkene, comprising: producing a gaseous halogen by decomposing a metal halide in a liquid, said liquid having a melting point below and a boiling point above the decomposition temperature of said metal halide;   reacting said halogen with a lower alkene to produce an alkyl dihalide gas; and   reacting said gas with a metal hydroxide to regenerate said metal halide and to produce a lower diol corresponding to said alkene.   
     
     
       17. The method of claim 16 wherein said halogen is bromine. 
     
     
       18. The method of claim 16 wherein said alkyl dihalide is passed through an aqueous solution of said metal hydroxide. 
     
     
       19. The method of claim 18 wherein said metal halide decomposes to produce a metal halide of a lower oxidation state which is later dissolved in water and oxidized to regenerate said metal halide and to produce said aqueous solution of metal hydroxide. 
     
     
       20. The method of claim 16 wherein said alkene has from 2 to 5 carbon atoms. 
     
     
       21. The method of claim 22 wherein said metal halide is ferric bromide, said liquid is molten, hydrated ferric chloride, and said metal hydroxide is ferric hydroxide. 
     
     
       22. The method of claim 21 wherein said gas is passed through an aqueous solution of ferric hydroxide. 
     
     
       23. The method of claim 22 wherein said solution is maintained at a temperature of about 40-80° C. 
     
     
       24. The method of claim 21 wherein said liquid is maintained at a temperature of about 110-280° C. 
     
     
       25. The method of claim 21 wherein said halogen and lower alkene are reacted at a temperature greater than about 40° C.